1. Field of the Invention
This invention relates to the field of shock cords (also known as Bungee cords) and rubber or rubber composite straps or cords and end pieces that are attached to the shock cords to secure the shock cord ends.
2. Prior Art
The common end configuration for a shock cord merely folds the end on itself and is held in place by a thick stiff wire clip. This folded shock cord end acts as a stop for a wire bale with a hook. The wire bale is usually tightly wound wire forming a sleeve through which the shock cord freely passes. The wire at the end of the wire bale is bent into a hook shape to make it easy to secure. The wire bale slide over the normally relaxed shock cord until the bale meets the folded end. Because the folded end is larger in diameter than the wire bale sleeve, the folded end acts a stop for the free movement of the bale. The wire clip holding the end of the cord folded on itself is very strong and creates a nearly permanent stop at the end of the cord. The wire clips holding the shock cord ends folded are difficult to install or replace. Therefore once a shock cord length has been chosen and the shock cord ends have been folded and secured with wire clips, the usable range of the shock cord is permanently set.
To use the shock cord, one end is secured, the cord is stretched, and then the other end is secured. When the tension of the cord is wrong, its points of attachment must be changed to accommodate the existing cord length or a shock cord of a different length must be used. In one known configuration a plastic hook piece has replaced the wire bale at one end of the shock cord. The plastic hook piece slides freely over the relaxed cord. At the desired length, the user bends the cord 180.degree. and forces the cord into a narrow slot, severely constricting the cord at that point. The free end of the cord is then pressed into a "jam cleat" type securing slot on the plastic hook piece to help prevent the cord from coming out of the slot into which it has been folded. Repeated or prolonged use of the plastic hook piece reduces the life of the cord as the highly constricting slot holding the cord severely pinches the cord at that point. This severe pinching action strains the cord excessively and damages it a little every time the plastic hook piece is attached, eventually resulting in premature failure.
The core of shock cords is an elastomeric substance. Elastomeric substances breakdown with time and exposure to the environment. A new shock cord that may have good tension for a particular application when new, will lose tension over time and may become unacceptable. The cord will then have to be replaced with another one having the desired tension, or the length could be adjusted, for example by using the plastic hook piece already described. The damaging effect of the plastic hook piece slot will soon cause the elastomer to fail and the cord to lose it shock absorbing qualities.